The present invention relates to a bag including an air bag, a water pillow, a cover, a float, and a life buoy, which is made of a resin sheet or film.
Among such types of bags, an air bag for use in restraining a vehicle occupant during collision has been typically made of woven fabric of fiber such as polyamide fiber with silicone rubber coating. As alternatives, an air bag made of heat-resisting resin sheet (JPA No. 2-31965) and an air bag made of elastomer (JPA No. 4-266544) were recently proposed.
Such heat-resisting resin sheets or elastomer sheets are cut out in desired sizes from a large sheet and then bonded together by adhesives or fusion.
The method of cutting out the sheets in desired sizes from the large sheet takes a lot of time, thereby lowering the productivity.
When the resin sheets are bonded together by adhesive or fusion defective bonded portions may be formed because of bulkiness and irregularity of the sheets.
It is an object of the present invention to provide a method of manufacturing a resin bag, whereby the peripheral edge of the bag such as a resin air bag is not bulky, the bonding strength is still sufficient, and the productivity is increased.
It is another object of the present invention to provide a resin bag which can be quickly inflated when a gas is supplied inside the bag.
A method of manufacturing a resin bag according to a first aspect is a method using an insert molding, the resin bag comprising two sheets, i.e. first and second resin sheets which are bonded to each other at least at one portion of the peripheries thereof. The method of manufacturing the resin bag comprises disposing the first resin sheet in a cavity of a mold, overlaying a heat-resisting sheet smaller than the first resin sheet on the first resin sheet to expose the periphery of the first resin sheet along the outer periphery of the heat-resisting sheet, and then injecting resin into the cavity in a state where the mold is opened, closing the mold with pressing and expanding the injected resin in such a manner that the injected resin covers the heat-resisting sheet and the exposed periphery of the first resin sheet, thereby molding the second rein sheet and bonding together the periphery of the second resin sheet and the periphery of the first resin sheet.
A method of manufacturing a resin bag according to a second aspect is a method using an insert molding, the resin bag comprising two sheets, i.e. first and second resin sheets which are bonded to each other at least at one portion of the peripheries thereof. The method of manufacturing the resin bag comprises disposing the first resin sheet in a cavity of a mold, overlaying a heat-resisting sheet, which is smaller than the first resin sheet and having an opening, on the first resin sheet to expose the periphery of the first resin sheet along the outer periphery of the heat-resisting sheet and to expose a portion of the first resin sheet corresponding to the opening of the heat-resisting sheet, then injecting resin into the cavity in a state where the mold is opened, closing the mold with pressing and expanding the injected resin in such a manner that the injected resin covers the heat-resisting sheet and the exposed periphery and the exposed portion, facing the opening, of the first resin sheet, thereby molding the second resin sheet and bonding together the periphery and the portion, facing the opening, of the second resin sheet and the periphery and the portion, facing the opening, of the first resin sheet.
In the above method, the second resin sheet is made of the resin injected into the cavity and the resin adheres the periphery of the first resin sheet not covered by the heat-resisting sheet or the periphery and the portion facing the opening of the heat-resisting sheet. The first resin sheet is covered by the heat-resisting sheet except the periphery or except the periphery and the portion facing the opening so that the covered portion is not in directly contact with the injected resin. Therefore, the resin is bonded to the exposed portions of the first resin sheet.
The resin bag of the present invention is composed of two resin sheets of which peripheries are bonded together and wherein at least one of the resin sheets has a rough surface facing the inside of the bag.
The bag is particularly suitable for an air bag. As at least one of the resin sheets has a rough surface facing the inside of the bag as mentioned above, the sheets are prevented from adhering to each other even when these are overlaid on each other for a long time, thereby preventing the bag from not opening.